It is known to carry out an unbalance measurement operation on a motor vehicle wheel by driving the motor vehicle wheel in rotation while it remains mounted on the motor vehicle and raised on a suitable jack device and thus is freely rotatably. The motor vehicle wheel can be driven by means of a friction wheel which in turn is driven by an electric motor, with the friction wheel being pressed against the motor vehicle wheel with varying pressure forces. A method of that nature, and a suitable apparatus for carrying out the method, are to be found in DE 38 28 724 A1 (corresponding to EP 0 355 304A2 and U.S. Pat. No. 4,956,998). That situation involves determining unbalances of the motor vehicle wheel on the motor vehicle. As indicated above, to assure that the wheel whose unbalance is to be measured, which comprises a disk wheel or hub and a pneumatic tire fitted thereon, is freely rotatable, the wheel can be jacked up by a suitable jack device. So that the wheel can be rotated at the required speed, the friction wheel driven by the electric motor is pressed against the pneumatic tire. In order to provide for a slippage-free transmission of drive from the friction wheel to the pneumatic tire, the operating procedure involves using two given pressures or contact forces between the friction wheel and the pneumatic tire, which represent switching threshold values for switching the drive motor, and therewith the friction wheel, on and off. The required pressure force is of such a magnitude that, when the system is switched on, the drive moment produced by the drive motor is transmitted in a slippage-free manner to the motor vehicle wheel. When the system is switched off, a reduced drive or braking moment is similarly transmitted without slippage to the motor vehicle wheel. Attaining freedom from slippage, in such a procedure, is difficult because the switching forces have to be established in dependence on the maximum motor moment or torque and the lowest frictional value between the friction wheel and the motor vehicle wheel whose unbalance is to be measured. In that respect, the drive moment or torque produced by the motor is generally dependent on a number of factors such as the speed of the motor, the operating voltage (at least about 360 V, with a maximum of about 440 V), and the motor temperature. The frictional value as between the motor vehicle wheel, specifically the pneumatic tire, and the friction wheel is also dependent, for example, on the state of the tire, for example whether it is wet or dry, and the like.